1. Field of the Invention
Optical brightening agents (OBAs) of the bis-(triazinylamino)-stilbene type are widely used to brighten natural and regenerated cellulosic fibres, natural and synthetic polyamide and polyurethane fibres, natural or synthetic pigment preparations, textiles and paper.
2. Description of Related Art
The use of high concentrations of optical brightening agents in coating applications can lead to the substrate taking on a greenish hue, particularly in cases where the coating formulation contains no synthetic binder.
One method which has been used to overcome this problem is to use a coating formulation containing a high proportion of a carrier such as a polyethylene glycol.
DE-2 335 570 A1 discloses bis-(triazinylamino)-stilbene derivatives in which both triazinyl radicals are directly substituted by polyethylene glycols. However, only short chains containing from 1 to 3 ethoxylated units are reported.
U.S. Pat. No. 6,596,864 B1 discloses bis-(triazinylamino)-stilbene derivatives in which both triazinyl radicals are substituted by polyethylene glycols having up to 35 ethoxylated units.
GB-997 175 A discloses bis-(triazinylamino)-stilbene derivatives in which both triazinyl radicals are substituted by polyetheramines. However, only short chains containing from 1 to 4 ethoxylated units are reported.